Continuous crank@key in - Page 2 - Chevy and GMC Duramax Diesel Forum
04.5-05 LLY Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

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post #11 of 20 (permalink) Old 08-28-2018, 08:00 PM
 
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Have a similar problem with my lly after washing the engine compartment. Key in, turn to first detent which should be acc, truck turns over and fires up as if you meant to start it. Happens about 50% of the time when washing under the hood. I believe the problem is when the fuse box gets wet it allows voltage to jump from one circuit to another. Always goes away after warmed up and dried out. Iím not the original owner so I canít say that thereís never been any accessories added and then removed. I have had the truck for the last 10 years and 120,000 miles.
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post #12 of 20 (permalink) Old 08-30-2018, 02:52 AM
 
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Man, this is super interesting, any update from OP? What happened with the new fusebox?
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post #13 of 20 (permalink) Old 08-30-2018, 08:41 PM
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J83. What should the voltage be on those pins u mentioned in your earlier post without the relay in. And with it in
there should be 12V between the 86 and 85 pins.

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post #14 of 20 (permalink) Old 01-04-2020, 01:55 PM
 
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Hi, we have a similar problem, but the starter engages when the key is moved to the run position. I checked the relay as you suggested and one of the pins, 86, has 9.4 volts in the run position which I am assuming is enough to energize the solenoid circuit. I also know that after starting in the run position, if I shut it off and immediately try to restart it, it will start correctly in the start position. If I start it after it has sit for a short period of time, it will start in the run position and if I shut it off and it sits for 15-20 minutes, it will start in the run position almost every time. I don't see anything wrong with any wiring, I have changed the ignition switch, the key/cylinder is not loose, so am I looking at a faulty ECM or as some have said it could be the TCM? Any suggestions would be appreciated.
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post #15 of 20 (permalink) Old 01-04-2020, 07:35 PM
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A big clue to me is the fact that stuff only happens when you wash it. Sounds like water is getting into a connector or the fuse box or somewhere where it's affecting electronics. Is there a chance this truck has been exposed to salt water or road salt and when you wash the truck it lets moisture into wiring? Saltwater can wreak havoc with electronics. I would start looking for water getting in somewhere, under the dash, hood, fuse boxes etc. There could be other issues caused by cobbled up wiring too...

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post #16 of 20 (permalink) Old 01-04-2020, 11:49 PM
 
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No, washing the truck has nothing to do with our problem, it starts when you turn the key to the run position, and we have determined that there is voltage to the start relay in the run position. Just wondering if this means that the ECM or TCM could be a problem, we have already changed the ignition switch, checked the wires, and the key/cylinder does not seem loose or a problem. Just need guidance as to what to check or do next.
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post #17 of 20 (permalink) Old 01-05-2020, 11:11 AM
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Has anybody thought about the pats system? I bet the alarm is cutting fuel and causing the truck not to turn over. Happened to me...

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post #18 of 20 (permalink) Old 01-05-2020, 11:13 AM
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The no communication with the obd2 port is the big ass fuses under the hood. IGN fuse... pull them out and put them back in. Could be a shit connection. If those fuses aren’t getting good contact he ecm will never see voltage hence the no communication. This has happened to me too...

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post #19 of 20 (permalink) Old 01-13-2020, 10:53 AM
 
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A big clue to me is the fact that stuff only happens when you wash it. Sounds like water is getting into a connector or the fuse box or somewhere where it's affecting electronics. Is there a chance this truck has been exposed to salt water or road salt and when you wash the truck it lets moisture into wiring? Saltwater can wreak havoc with electronics. I would start looking for water getting in somewhere, under the dash, hood, fuse boxes etc. There could be other issues caused by cobbled up wiring too...
Found the problem, the Transmission Control Module had a short in it!
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post #20 of 20 (permalink) Old 01-13-2020, 11:17 AM
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Hi, we have a similar problem, but the starter engages when the key is moved to the run position. I checked the relay as you suggested and one of the pins, 86, has 9.4 volts in the run position which I am assuming is enough to energize the solenoid circuit. I also know that after starting in the run position, if I shut it off and immediately try to restart it, it will start correctly in the start position. If I start it after it has sit for a short period of time, it will start in the run position and if I shut it off and it sits for 15-20 minutes, it will start in the run position almost every time. I don't see anything wrong with any wiring, I have changed the ignition switch, the key/cylinder is not loose, so am I looking at a faulty ECM or as some have said it could be the TCM? Any suggestions would be appreciated.


To better diagnose the issue, what you should do it make a table like the following. where P is the thick pink ignition wire, Y is the thick yellow ignition wire, O is the thick orange ignition wire and W is the thick white ignition wire.

Put a meter on each wire, and record the reading you get in the off position, accessory position (1 click after off and before run), the value in the run position, and the value while you have the key in the crank position (may want to pull the starter relay to prevent cranking the starter)

__________|-W-|-Y-|-P-|-O-|
Off ----------|
Accessory --|
Run ---------|
Start --------|


You should get the following table if everything were to be working correctly in the ignition switch.

00,00,00,00
00,00,00,12
12,00,12,12
12,12,12,00

Volts.


If your table differes from that, you should disconnect the ignition switch connector from the truck (there is a harness with a 7MM bolt that connects the harness from the ignition switch to the truck, disconnect this to isolate the truck from the switch)

Repeat the test above, if you get the correct values, the switch is working, and something after that connector on the truck side is screwed up, if you get the same incorrect values, then the ignition switch probably needs to be replaced.

NOTE: white and pink MIGHT have power in the accessory position, this would not cause your issue and should be considered "normal" for the purpose of this test. I cant 100% remember off the top of my head if GM treats them as true ignition wires, or as accessory wires that dont drop out in crank.
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